Hollow bodies which are held in a stable position by a continuous feed of air by means of a blower and in which there is admittedly a given positive pressure but which are not inflated as that air can escape again at least one location are frequently used for advertising purposes. By way of example DE 94 07 294 U discloses an advertising tube, which is 3 meters in diameter and 27 meters in height. An additional water container is provided in the region of the ground in order to achieve the necessary stability in relation to the ground while cables, which can be anchored to the ground for guying purposes extend to about three quarters of the height of the hollow body.
Recent times have seen the organisation of aerobatic flying competitions in which the aircraft must fly a course which is defined by overdimensional ‘slalom gates’. The gates comprise two ‘slalom poles’ which are set up at a spacing of for example 10 to 14 meters and which are 18 meters in height. The gates have to be negotiated in accordance with given rules, which are not essential here.
The individual slalom poles are hollow bodies of the kind set forth in the opening part of this specification which are not cylindrical but conical, wherein the hollow body axis extends inclinedly so that the generatrices, which define the gate, of the two hollow bodies are in mutually parallel relationship. The hollow bodies are composed of a plurality of flexible material webs comprising a material, which tears immediately when it comes into contact with a part of the aircraft. That means that there is no resistance such as to endanger the aircraft and the damaged hollow body collapses into itself and is replaced by a new one.
Fixing to a support foundation is implemented by way of guying cables which can only be arranged up to a low height above the ground (about two to two and a half meters) so that the stability which is to be achieved exclusively by the positive air pressure hitherto entailed problems, in particular as the hollow bodies must withstand wind speeds of up to 50 kph. Guying cables, which are fitted further up would endanger the aircraft.